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After taking the natural logarithm of both sides of Equation 1 twice, the linear regression equation is given as12-13


: Eqn. 2


plane. As far as aluminum castings are concerned, the value of X for relatively low (<1%) probabilities of failure under stress basically relates to m (see 14, 15, 16


The Weibull modulus, m, is the slope of the regression line between Y and the natural logarithm of the UBS, namely X for simplicity, and -mln(σ0


). In congruence, m


is usually taken as a measure of engineering reliability for a given cast product.


) is the Y-intercept in the X-Y


(a)


(b)


Figure 20. In-weld fracture of sample B-C1 after bend testing: (a) Surface of sample, which was in contact with bottom forces; (b) Crack adjacent to the fracture surface.


(a)


(b)


(c)


Figure 21. Regions of porosity located on the fracture surfaces of bend test specimens: (a) B-A1 pore at 700x magnification; (b) B-4 pore at 200x; (c) two pores near edge of B-4 at 100x.


78 International Journal of Metalcasting/Spring 2012


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